JP3499789B2 - Method for producing fish gelatin - Google Patents

Abstract

The preparation of fish gelatin is new and comprises gelling the skins of fresh or defrosted raw fish, washing the skins and treating them to acid extraction at high temperatures and at an acidic pH.

Description

Detailed Description of the Invention

[Prior Art and Problems to be Solved by the Invention] Gelatin is a protein of animal origin which has been known for many years, and has many applications in food, medicine, photography and technical fields.

Gelatin, in the form of its natural precursor, collagen, is widespread in animal tissues and organs such as skin and bone.

Gelatin is commercially obtained from bovine and porcine bones and hides recovered from slaughterhouses.

In both the United States and Europe, beef consumption has declined over the years and the supply of bone and skin from this source has diminished. This phenomenon has been exacerbated in recent years by bovine spongiform encephalopathy and the resulting regulation.

As far as gelatin from pigs is concerned, pigs have been found, for example, by the discovery of new outlets for this starting material, such as pork clutches and aperitifs snacks, and by religious considerations that prohibit the use of pigs in certain countries. The development of derived gelatin is limited.

Therefore, it is particularly important to look for other starting materials which can be used for the production of gelatin.

Fish skins, scales and bones have long been known to contain collagens similar to those found in mammals.

Patent GB 235,635 relates to the production of fish glue, gelatin and meat from marine-derived by-products. This mainly includes treatment of these by-products with alkali, followed by treatment with sulfurous acid to remove volatile bases responsible for fishy odor and treatment with water. However, there is no description of the by-products used, the extraction conditions or the characteristics of the resulting gelatin.

In order to respond to consumer demand for high quality fresh produce, especially fish fillets, the fishery and canning industries require fish to be landed as soon as possible after they are caught or after they have been thawed. Has been developing fillets for several years. This has made available certain amounts of fish by-products, especially fish skins, which could potentially be processed into gelatin.

Specifically, this is done by NORLAND PRODUCTS, which has produced an aqueous solution of fish gelatin by acid extraction of cod skin since 1985. However, the corresponding gelatin can be obtained under the usual conditions for measuring the gelling strength of gelatin (see “The Science and Technology of Gelatin”, 1).
977 A. G. Ward and A. Coats (C
OURTS), Academic Press, p. 507), according to the Bloom's method, a 6.67% gelatin solution maintained at 10 ° C for 17 hours). It remains liquid even when it is at a height of 45%.

Other processes have been developed to improve the quality of products obtained from fish skin. Patent EP 0436266
Process includes a step involving treatment with a dilute base, followed by washing and treating with a different acid. Furthermore, gelatine is preferably neutrally extracted at temperatures between 40 and 50 ° C.

More recently, US Pat. No. 5,484,888 reports a process for the preparation of gelatin from "kosher" fish skin, ie with scales and fins.

The process described in the above patent is carried out entirely in alkaline medium. The first step involves soaking the hide in an alkaline solution for 3 to 60 days. The extraction is also at alkaline pH, preferably pH 10 at 45 and 55 ° C.
At a temperature between. Finally, the above patent
It is believed that tuna rind is not suitable for gelatin production because of the boiling pretreatment it is exposed to.

[Means for Solving the Problems] Accordingly, the present invention relates to an acidic process for preparing high-quality gelled fish gelatin from fish or thawed raw fish skin, which comprises washing the skin with water and treating with acid. And heat extraction at acidic pH.

The starting material consists of the skin of fresh or thawed fish obtained in large quantities when the fish is treated raw.

[0016] Specifically, "tuna in salt water (t
una in brine) ”.
other fish such as (sole), tilapia, and catfish, especially the “channel catfi
sh) ”, a freshwater species called Ictalurus punctatus,
This is also the case when the raw fillets are on the market in large quantities.

According to one preferred characteristic, the fish skin is, for example, tuna, tilapia, carp, Nile perch.
perch), salmon, sole, in particular tropical sole, pollack, hake, mackerel or other similar fish such as scales and fins.

According to another feature of the invention, the fish skin is, for example, a catfish, in particular a "channel catfish".
, A freshwater species called Ictalurus punctatus, or other African Sea catfish, or a non-scale fish such as young or North African catfish.

The fish fillets obtained after dropping the head and removing the internal organs are cut and peeled by hand or machine, leaving the fillets on one side and the skin on the other side. At this stage, the skin can be harvested and washed, and immediately frozen for later use.

The skin may be used as it is or may be partially dried to a solids content of about 65 to 75%, or may be in the form of small pieces as a whole, eg about 10 to
It can be used as a piece with a size of 30 cm or ground into pieces with a size between about 5 mm and 15 mm.

In the process of the present invention, the skin is first washed with water to remove unwanted compounds such as blood and fat.

[0022] Advantageously, fresh or thawed skin is easy to process and if washed with water is slightly oxidized media
It has been found that a gelatin with improved characteristics is obtained if carried out in a zing medium).

This in fact makes it possible to act on very large amounts of microbial flora within the mucous membranes of the skin. Thereby, the odor-causing bacterial decomposition phenomenon is prevented or at least delayed, but the starting material is not decomposed.

"Slightly oxidizing medium" is understood to mean an aqueous solution of an oxidizing agent, the oxidizing agent being 50 to 1000 ppm.
It exists in concentrations on the order of (0.005 to 0.1%).

An oxidizing agent that can be used is, for example, hypochlorous acid.
Salt type, specifically sodium or potassium hypochlorite, or hydrogen peroxide.

After this washing, the skin swells, aids in the removal of unwanted compounds and is immersed in a cold acid bath with stirring in preparation for the extraction of gelatin.

The judicious combination of reaction parameters such as the nature of the acid, the amount of acid and the time makes it possible to extract gelatin in satisfactory yields without mechanical degradation of the skin.

Mineral acids such as hydrochloric acid, sulfuric acid or phosphoric acid are used at a rate of 3 to 20 L per tonne of fresh rind, or organic acids such as acetic acid or lactic acid at the above-mentioned rates. Would be preferred.

The duration of the acid treatment is, for example, 1 to 8
It will be of the order of hours, preferably about 4 hours.

After the acid bath, excess acid is removed by washing with water and the pH is adjusted to a value below about 5.

By using this preparation, under thermal conditions not heretofore described, in particular above 50 ° C., there is virtually no loss of character and, in particular, the retention of high gelling strength. It has also been found that the skin can be subjected to extraction at a temperature, for example on the order of 55 ° C to 70 ° C.

According to the invention, the extraction is carried out in an acidic medium with a pH below 5, preferably in the order of 2.5 to 4.5.

Preferably, for example, after 4 to 6 hours, the gelatin titer (ie extraction broth).
The extraction is stopped when the gelatin concentration in the broth) is on the order of 4-5%.

The medium is then separated by settling to give a gelatin solution and a solid residue. Advantageously, it is possible to purify a solution of fish gelatin without exposing the starting material to the alkaline treatments described in the literature, in particular to remove traces of compounds responsible for fish odor and flavor. That was discovered.

To do this, after extraction, it is filtered in the presence of a filter such as diatomaceous earth. Filtration can optionally be carried out on a plate filter type device to retain traces of fat and obtain the desired clarity. The filtered solution is then passed through an ion exchange resin to reduce the ionic value and immobilize any fish degrading compounds such as amines and amine derivatives, after which the pH is adjusted to values in the range 5-7. Finally, the filtered gelatin solution is desalted and concentrated under high vacuum to remove volatile odors and further improve the odor of the product.

Interestingly, finally, the residue obtained after precipitation of the extraction broth also gives a small amount of non-gelled fish gelatin by adding water and heating at a temperature of about 95 ° C. for about 2 hours. I found that.

In this way, the process according to the invention results in a predominantly high quality gelled fish gelatin without fish flavor or odor. The process of the invention is applicable to all fish skins, their properties merely modifying the gelling strength obtained. The process of the present invention also provides small amounts of non-gelling gelatin as a by-product.

EXAMPLES The invention is illustrated by the following examples without imposing a limitation.

Example 1 4.5 kg of frozen tuna skin is thawed at room temperature. The skin obtained is then cut to a size on the order of 20-40 cm. The cut rind is immersed in a first wash bath containing 15 L of water oxidized by the addition of 14 mL of a sodium hypochlorite solution of density 1.2 for 20 minutes with stirring. After draining, clean water 11.5
Add more L and continue stirring for 15 minutes. The second bath is then drained.

An acidic bath is then prepared by adding 6.7 L of water, followed by the addition of 46 mL of concentrated sulfuric acid (96%). The duration of this bath is of the order of 5 hours with intermittent stirring. At the end of this bath, the acidic solution is drained and then the skin is washed with 3 × 15 L of water, each lasting about 1 hour.

The skin thus prepared is placed in a reactor, and 15 L of 90 ° C. hot water is introduced therein. The solution in the reactor has a pH between 3.5 and 4.0 and is maintained at 58-60 ° C by circulation with an external heat exchanger. After 4 hours of extraction the gelatin titer is of the order of 4%. The reaction broth is then discharged and contains 640 g equivalent of gelatin.

The reaction broth is centrifuged and then filtered with the aid of diatomaceous earth on an AMAFILTER type device.

Next, the clear solution of fish gelatin was desalted by passing it through an ion exchange resin, and the p
Adjust H between 5 and 7.

The solution is evaporated under vacuum and concentrated to a concentration of between 25 and 30%. The concentrated solution is then gelled,
Dry by conventional methods.

This gives 605 g of dry fish gelatin with a gelling strength of 198 Bloom and a viscosity of 3.8 mPa.s.

Example 2 2 kg of tilapia skin are thawed as in Example 1 and then washed twice with water before being treated with a 3 L sulfuric acid bath of water containing 8.5 mL sulfuric acid per kg of fish skin for 4 hours. The skin thus prepared is then washed with water, Example 1
Extracted as well as gelled strength 264 Bloom and viscosity 2.1
214 g of fish gelatin with mPa.s are obtained.

Example 3 3 kg of catfish (Ictalurus punctatus sp.) Or "channel catfish" skin was thawed in the same manner as in Example 1 to give a gelling strength of 217.
337 g of fish gelatin with a bloom and a viscosity of 1.7 mPa.s are obtained.

Example 4 3 kg of mackerel skin was thawed, treated in the same manner as in Example 1, and gelled.
Fish gelatin 190 with 130 bloom and viscosity 3.5 mPa.s
g is obtained.

Example 5 2.6 kg of tuna skin is thawed at room temperature. The skin obtained is then cut into small pieces with a size of 20 to 40 cm. The cut skin is immersed for 20 minutes with stirring in a first wash bath containing 9 L of water oxidized by the addition of 8.5 mL of a sodium hypochlorite solution of density 1.2. After draining, add another 7 L of clean water to create a second bath and stir for 15 minutes.

Then, after discharging, 6 L of water and then glacial acetic acid
Prepare the acidic bath by adding 28 mL. The duration of this bath is of the order of 5 hours with intermittent stirring. When the bath is finished, the acidic solution is drained off and the skin is then washed with 9 L of water for 1 hour.

After discharging, the rind was placed in a reactor, and 8 L of hot water at 90 ° C was introduced. The solution in the reactor has a pH between 4.5 and 5
And maintained at 55 ° C for 4 hours by circulating through an external heat exchanger. After 4 hours, the gelatin titer is 3.8%
Is the order.

The broth is then discharged and the centrifugation, filtration, desalting, evaporation, gelling and drying operations are carried out as described in Example 1.

This gives 323 g of dried fish gelatin with a gelling strength of 266 Bloom and a viscosity of 3.9 mPa.s.

Example 6 The same procedure as in Example 5 except that lactic acid was used instead of acetic acid for the acidic bath. This gives 294 g of gelatin with a gelling strength of 260 bloom and a viscosity of 3.8 mPa.s.

Front Page Continuation (72) Inventor Richard Bialot France, 16000 Angleum, Liu Sictimy, Residens Bohlgar-Batiman Ohm (no address) (72) Inventor Georges Takkerkar France, 92130 Issy- Laem Reinault, Esplanade Raoul-Fourlot, 19 (72) Inventor Jackie David, France, 84800 Isul-Sour-Sorgue, Schmanns de Peilla, 165 (56) Reference JP-A-3-209395 ( JP, A) JP-A-2-65747 (JP, A) International Publication 98/017738 (WO, A1) Wakayama Industrial Technology Center Research Report, Japan, 1993, Vol. 1992, pp. 1-3 (58) Fields investigated (Int.Cl. ⁷ , DB name) A23J 1/00-7/00 JISST file (JOIS)

Claims (24)

(57) [Claims] 1. A method for producing gelled fish gelatin from fresh or thawed raw fish skin, said method comprising:
The method comprises the following steps: a) In order to prevent bacterial decomposition of the fish skin,
Pieces of fresh or thawed raw fish skin as a whole
50 to 1000 ppm , in the form of
Aqueous solution of oxidizer present in a concentration of ( 0.005 to 0.1 %)
In step washing; b) a step of treating said washed skin with acid; and, then
And c) from said fish skin at temperatures above 50 ° C. at acidic pH
A method comprising the step of extracting gelatin; wherein the method does not include an alkali treatment step. 2. The method according to claim 1, wherein the fish skin is used as it is or partially dried. Wherein the oxidizing agent The method of claim 1 selected from hypochlorite and hydrogen peroxide. 4. The hypochlorite is sodium hypochlorite.
The method according to claim 3, which is um or potassium hypochlorite. 5. any one of the methods of claims 1 to 4 used for the mineral acid or organic acid is the acid treatment. 6. The method according to claim 5 , wherein hydrochloric acid, sulfuric acid or phosphoric acid is used as the mineral acid, or acetic acid or lactic acid is used as the organic acid. 7. The acid is 3 to 20 per ton of fish skin.
The method according to claim 5 or 6 , which is used for a ratio of L. Wherein said acid treatment is 1 to 8 hours The method of any one of claims 1 to 6 is performed. 9. The acid treatment is carried out for 4 hours.
the method of. 10. The method according to claim 1, wherein the extraction is carried out at a pH below 5. 11. The extraction at a pH between 2.5 and 4.5
11. The method of claim 10 performed. 12. The extraction process of any one of claims 1 to 11 carried out at a temperature higher than 50 ° C.. 13. Extraction at a temperature between 55 ° C. and 70 ° C.
13. The method of claim 12, which is performed in degrees. 14. A method comprising the steps of purifying and desalting the gelatin solution obtained by extraction.
13. The method according to any one of 13 above. 15. The gelatin solution obtained by extraction is treated with diatomaceous earth and then filtered.
14 ways. 16. The method according to claim 14 or 15, wherein the filtered gelatin solution is desalted on an ion exchange resin and then adjusted to a pH of 5 to 7. 17. The filtration and desalting gelatin solution, subsequently concentrated under vacuum, volatile odor is removed, then a claim 14 which is solid and drying
The method according to any one of 16 above. 18. The method according to any one of claims 1 to 17 , wherein the fish skin is fresh fish-derived raw skin, which has been peeled, washed and immediately frozen. 19. The method of claim 18 , wherein the skin is from a fish having scales and fins. 20. The method of claim 19 , wherein the fish is selected from tuna, tilapia, nile perch, salmon, sole, carp, pollack, hake and mackerel. 21. The fish is a tropical sole.
Item 20. 22. The method of claim 21 , wherein the skin is from a scale-free fish. 23. The method of claim 22 , wherein the fish is a catfish. 24. The catfish are channel catfish,
The Frika sea catfish or North American catfish.
Method 3